Fluid pressure operated magnetic switch



v WIN n J Oct. 27, 1970 c. w, ALLEN 3,536,875

FLUID PRESSURE OPERATED MAGNETIC SWITCH Filed Oct. 17, 1967 f w v I INVENTOR CLiFFORD WALLEN AT TOR NEY United States Patent 3,536,875 FLUID PRESSURE OPERATED MAGNETIC SWITCH Clifford W. Allen, Lexington, Ky., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Filed Oct. 17, 1967, Ser. No. 675,857 Int. Cl. H01h 35/34 US. Cl. 200--83 7 Claims ABSTRACT OF THE DISCLOSURE A bar magnet disposed adjacent an electrical switch polarizes a pair of normally spaced magnetizable members in the switch into mutually attractive engagement, thereby closing the switch. A third magnetizable member displacable from the magnet by expansion of an inflatable bag member or balloon is moved into abutting relationship with bar magnet upon deflation of the bag member to thereby shunt the magnetic field of the magnet, and thus effect depolarization of the pair of magnetizable members which thereupon spring apart to assume the open switch "condition.

The increasing commercial utility of pure fluid devices, that is, devices in which a first fluid flow within the device is affected by fluid contact with a separate controlling fluid flow within the device, has given rise to the need for a fluid pressure operated switch which will effectively convert the customarily low fluid pressure output signal of these devices (on the order of 1 p.s.i.) to an electrical signal.

Accordingly, it is the object of this invention to provide a simply constructed, highly sensitive electrical switch that if effectively operated in response to low pressure changes or signals.

In the present invention, this object is achieved by providing in a housing a bar magnet disposed adjacent to an electrical switch comprising a pair of elongated flexible electrical conductors corelatively disposed in parallel axial alignment with their free inner ends in partial axially overlapping relationship, mounted within a capsule with the outer ends of the conductors attached to and extending through the opposite ends of the capsule, each outer end of one of the conductors connected to a different one of a pair of electrical terminals extending through one end of the casing for plug-in operation with a pair of corresponding terminals in an electrical circuit. When the electrical conductors are in their unflexed conditions, the overlapping inner ends thereof are spaced apart, thus disposing the switch in the open condition. However, the bar magnet fixed to the housing adjacent to and in substantially axially parallel relationship with the conductors has a magnetic field of such strength and in such position as to normally engulf the conductors and oppositely polarize them into mutually attractive relationship effecting flexing of the conductors into mutual engagement, thus closing the switch. An elongated magnetizable member in the housing is disposed for pivotal movement in a limited path between opposing guide members so as to move in a first direction to engage the bar magnet, thus shunting or displacing its magnetic field away from said conductors and thereby effecting a relative depolarization of the conductors which, because of the weakened magnetic field therethrough, spring apart by virtue of inherent bias to open the switch. Alternatively, the member may be moved in the reverse direction to a point displaced from the bar magnet so that the magnetic field of the bar magnet returns to its first position to repolarize and thereby flex the conductors into engagement. The aforementioned movement of the magnetizable member is effected by an expansible bag member, or balloon, disposed between a portion of the housing and the magnetizable member and having a neck protruding through the housing for connection to a lower pressure source, such as the output of a pure fluid device, Whereupon the application of a low pressure within the balloon inflates it to apply a force to the magnetizable member overriding the force of the magnetic field thereon to move the member away from the bar magnet, and whereupon deflation of the balloon permits the magnetic field of the bar magnet to draw the elongated member into reengagement with the bar magnet, thus shunting the magnetic field of the bar magnet to weaken the strength of the magnetic field through the conductors.

This and other objects will be apparent in the following specification taken with the drawing, in which:

FIG. 1 is a top plan view of a fluid pressure operated switch showing the invention;

FIG. 2 is a sectional view of the switch taken substantially along the line 2-2 of FIG. 1;

FIG. 3 is a sectional view of the switch taken substantially along the line 3-3 of FIG. 2;

FIG. 4 is a diagrammatic view of the switch showing the theoretical operation of the device to open the electrical switch; and

FIG. 5 is a diagrammatic view of the device showing the theoretical operation of the device to close the electrical switch.

Referring now to FIGS. 1, 2 and 3 of the drawing there is shown a housing comprising a pair of members 1 and 2 constructed of any suitable material such as plastic, which, when attached together by any suitable means, such as screws 3, provide a cavity 4 therebetween for containing all the prime elements of the fluid pressure operated switch. These prime elements generally comprise a bar magnet 5 fixed as by bonding a pair of supports 6 which may be integral with housing member 2, an encapsulated electrical switch 7 secured as by bonding within a well 8 in housing member 2, an elongated magnetizable member 9 pivotally movable within cavity 4 to engage and disengage one end of the member relative to the bar magnet, and an inflatable bag or balloon 10 disposed between the housing 2 and the elongated member, and which, when expanded, raises the elongated member to disengage and displace the same relative to the bar magnet.

The aforementioned electrical switch 3 comprises an elongated capsule 11, which may be constructed of any suitable material such as glass, having disposed therein the free ends of a pair of elongated axially parallel electrical conductors 12 and 13 comprised of any suitable, electrically conductive flexible and magnetizable material, such as iron or steel. Each conductor 12 and 13 is connected at one end of the inner end of a different one of a pair of terminals 14, 15-, respectively, which extend from cavity 4 through one end of the housing for external plugin connection into an electrical circuit, not shown. From the terminals, the conductors pass through opposite sealed ends of the capsule with their free ends disposed within the capsule in slightly axially overlapping relationship so that when the conductors are in their unflexed condition, they normally assume a spaced apart relationship, which spacing may be either vertical or horizontal depending upon a matter of choice only, so that the switch is in the open condition, thus interrupting any current flow between the terminals. Alternatively, when the conductors are flexed into mutual engagement, the switch is closed to provide current flow between the terminals 14 and 15,

The aforementioned elongated magnetizable member 9 preferably may be comprised entirely of any suitable 3 magnetizable material, such as iron or steel, as shown, but, if desired, the member may be comprised of a nonmagnetizable material, such as beryllium-copper, equipped with a magnetizable tab, not shown, comprised of a material such as iron or steel, which tab overlies the bar magnet. The member 9 is disposed to longitudinally overlie the aforementioned balloon with one end overlying the bar magnet and with the remote end attached to the housing members to longitudinally fix the member 9 relative to the balloon and bar magnet and provides for vertical movement of the one end within cavity 4 relative to the bar magnet 5 in response to inflation and deflation of the balloon, with lateral movement of the magnetizable member being limited by a pair of oppositely disposed guide members 16, 17 which may be formed integral with either of the housing members 1 and 2 or which may comprise separate members disposed between housing members 1 and 2 and attached to one or both of the housing members by any suitable means, such as axially extending dowels, not shown, on the guide members fitted into corresponding holes in the housing members 1 and 2.

If desired, the remote end of member 9 may be fixedly attached to the housing so that the member 9 comprises a spring member flexible upwardly by balloon inflation with inherent spring return upon balloon deflation. Preferably, however, as shown in the drawing, the remote end of the member 9 is loosely pivoted in the housing members to minimize the fluid pressure required to raise the one end of the member relative to the bar magnet, the pivot means comprising a pair of laterally opposed notches 18 near the remote end of member 9, each notch loosely engaging one of a pair of vertically disposed pins 19, respectively, which pins are integral with the housing member 2 with their distal ends received in corresponding holes in the housing member 1. The remote end of the member 9 is provided with an arcuate notch 20 straddling the balloon with clearance during inflation and deflation of the balloon to eliminate any counterrotational force on the member 9.

If desired, a tab 21 may be included on the underside of the magnetizable member 9 to facilitate an assist to deflation of the balloon and institute immediate rise of member 9 when the balloon is inflated.

The inflatable bag or balloon 10 is formed in the shape best shown in FIG. 3 and is comprised of any suitable material such as rubber. The neck 22 of the balloon protrudes through a suitable aperture at the end of the housing opposite the terminals 14, and is held in a radially distended manner, for easy ingress of fluid to the balloon body, by a tubular member 23 comprised of any suitable rigid material and partially inserted in the neck, with the tube having an annular rib or radial extension 24 over which the balloon neck 22 is sleeved, which radial extension is axially and radially seated within an annular cavity 25 in the aforementioned aperture to thus position the balloon within the housing. The outer end of the tube facilitates easy connection of the balloon to a source of fluid pressure, not shown.

In now describing the operation of the above-described device, reference is made to FIGS. 4 and 5 which diagrammatically illustrate the theoretical interaction between the bar magnet 5, the magnetizable conductors 12 and 13, and the magnetizable member 9 as viewed from the right of FIG. 2. The relative sizes and positions of these elements are different from those of FIGS. 1, 2 and 3 for the convenience of clearly illustrating the operating principles.

The FIG. 4, showing the magnetizable member 9 disposed in its lower position in engagement with bar magnet 5 when the balloon 10 is deflated as shown in FIG. 1 of the drawing, the magnetic lines of force 23, illustrating the principal location of the magnetic field of bar magnet 5, are displaced primarily through magnetizable member 9, thus eliminating or greatly diminishing the magnetic field which, but for the immediate presence of member 9, would pass through conductors 12 and 13 to oppositely polarize them into a mutually attractive condition overriding the inherent bias of the conductors to urge them into mutual contact. Accordingly, in FIG. 4, the magnetizable member 9 acts as a shunt for the magnetic field of the bar magnet relative to the conductors 12, 13 to effect opening of the switch.

In FIG. 5, showing the raised position of the magnetizable member relative to the bar magnet, which position is assumed when the balloon 10 is inflated, the relatively remote position of the member 9 with respect to the bar magnet substantially reduces the above-described shunt for the magnetic field, which field accordingly shifts to more densely engulf the magnetizable conductors 12 and 13 to oppositely polarize them, as indicated by the north and south pole designations N and S, respectively, by an amount suflicient to provide mutual attraction overriding the inherent bias to cause the conductors to flex into engagement, thus closing the switch 3. It is to be noted, however, that although the raised position of member 9, as illustrated in FIG. 5, reduces its shunting action upon the magnetic field of the bar magnet, member 9 may nevertheless remain in the outer limits of the magnetic field which then operates to attract member 9 to the bar magnet upon deflation of the balloon, thus providing a bias for returning the member 9 to the position shown in FIGS. 1 and 4.

The foregoing structure is ideally suitable to the construction of a highly sensitive switch responsive to very low pressure signals. However, it is readily apparent that these same principles may be applied to larger heavy duty devices for switching larger currents in response to higher fluid pressure signals, as desired, without departing from the invention.

Having now described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. A fluid pressure operated magnetic switch, comprising:

(a) a housing having a cavity therein;

(b) a pair of normally disengaged conductors in said cavity, each having one end fixed to and extending through said housing for connection to an electrical circuit;

(c) a bar magnet fixed to said housing adjacent said pair of conductors and having a magnetic field normally having a first position for polarizing said conductors into mutually attractive engagement;

((1) pivot means, a magnetizable lever member dis posed in said cavity in pivotal relation with said pivot means and selectively movable about said pivot means to a first position engaging said bar magnet to shunt said magnetic field to a second position away from said pair of conductors and movable to a second position about said pivot means away from said bar magnet to permit return of said magnetic field to said first position; and

(e) an expansible bag member disposed between said lever member and the wall of said cavity, which, when expanded by the application of fluid pressure therein, moves said lever member about said pivot means from said first to said second position.

2. A fluid pressure operated magnetic switch, as recited in claim 1, in which said expansible bag member comprises a balloon.

3. A fluid pressure operated magnetic switch, as recited in claim 2, in which:

(a) said housing includes an aperture having a radial cavity therein;

(b) said balloon includes a neck extending through said aperture in said housing; and

(c) a rigid tubular member is disposed with said neck and axially extending through said aperture, said tubular member having a radial protrusion thereon distending a portion of said neck into mating relation within said radial cavity in said aperture to fix said balloon to said housing and maintain said neck in an open condition.

4. A fluid pressure operated magnetic switch, as recited in claim 1, in which said magnetizable member when moved to said second position is biased by said magnetic field toward 'said bar magnet so that upon relief of pressure in said expansible bag member said magnetizable member will move to said first position.

(0) a bar magnet fixed to said housing adjacent said 5. A fluid pressure operated magnetic switch, as recited in claim 1, in which a portion of said magnetizable member intermediate its ends includes a tab engaging a portion of said expansible bag member to assist in deflation of said expansible bag member and effect immediate movement of said member when said expansible bag member is inflated.

6. A fluid pressure operated magnetic switch, comprising:

(a) a housing;

(b) a magnetic switch in said housing;

(c) said magnetic switch including a member mounted in said housing for movement from each of two positions to the other, one of said two positions effecting closing of the switch, and the other of said two positions effecting opening of the switch;

(d) means biasing the member to one of said two positions;

(e) expansible bag means having a neck and disposed between said member and said housing, which, when expanded by fluid pressure therein, moves said member to the other of said two positions;

(f) an aperture in said housing;

(g) a radial cavity in said aperture;

(h) said neck extending through said aperture;

(i) a rigid tubular member disposed internally of said neck and disposed axially within said aperture and having a radial protrusion thereon distending a corresponding portion of said neck into mating relation with said radial cavity to fix said expansible bag means to said housing and maintain said neck in an an open condition.

7, A fluid pressure operated magnetic switch, as recited in claim 6, in which:

(a) said housing is comprised of two mating. sections;

and

(b) each of said sections includes a different portion of said aperture.

References Cited UNITED STATES PATENTS 2,514,630 7/1950 Downing 200-83.6 X 3,201,537 8/1965 Klatte et a1. 335-205 X 3,206,572 9/196-5 Buehler ZOO-83.6 3,226,506 12/1965 Angrisani 335205 3,247,341 4/1966 Kizilos 20083.2 3,406,267 10/1968 Kohls ZOO-61.41 2,869,475 1/1959 Bobo ZOO-83.6 3,271,708 9/1966 McCormick 335-205 ROBERT K. SCHAEFER, Primary Examiner R. A. VANDERHYE, Assistant Examiner US. Cl. X.R. 20081; 335205 

